A cryogenic dewar is a vacuum insulated vessel designed to store liquid nitrogen at minus 196 degrees Celsius for extended periods with minimal evaporation. In an IVF clinic it is the primary storage vessel for frozen embryos, oocytes, sperm samples and ovarian tissue. Dewars come in a range of sizes from small 10 litre units used for sample transport up to 300 litre plus vessels used in high volume storage programmes. Vapour phase dewars, where samples are stored above the liquid nitrogen surface rather than submerged in it, are increasingly preferred in UK fertility clinics as they reduce cross contamination risk. For cryogenic dewars and storage equipment suited to UK IVF clinics visit Cryolab.co.uk.